Ht-7 is probably the acupuncture point mostly identified with treating anxiety. In their paper published last May in Neuroscience Letters, Zhao et al. shed some light on the molecular mechanism in the brain underlying the activity of Ht-7 as we know it from Chinese Medicine treatments.

The scientists studied rats that underwent an ethanol withdrawal procedure that caused them to be in an anxious state. Following anxiety induction, the rats were treated with acupuncture: they were divided into 3 different groups each received bilateral acupuncture either in Ht-7, Pc-6 or a non-acupoint. The rats' brains were analyzed by molecular methods at two time points: during the anxious state and after the acupuncture treatment. The scientists focused on the effect of acupuncture on Neuropeptide Y, a neurotransmitter found in the brain and in the autonomic nervous system of humans and other animals. Neuropeptide Y has several functions in the body and is mostly investigated due to its activity in increasing food intake and reducing stress. The levels of Neuropeptide Y were measured in the rats' amygdala, an almond-shaped set of neurons which form part of the limbic system in the brain. The amygdala plays a key role in the processing of emotions and it regulates the emotional response to stress. The measurements showed that Neuropeptide Y levels were significantly reduced during the rats' anxious state as compared to their basal state. The anxious rats were then treated with acupuncture once daily for 1 minute at acupoints Ht-7, Pc-6 or a non-acupoint over 3 days. The acupoints in rats were equivalent to those in human subjects and in animal acupuncture references. The scientists measured Neuropeptide Y levels again to find out whether there is an effect of any of the points on the neurotransmitter levels in the amygdala. Their results were conclusive: the reduction in the Neuropeptide Y protein level at the anxious state was reversed by treatment at Ht-7. However, this reversal was absent in the groups that received acupuncture at PC6 and non-acupoints. Moreover, the treatment exerted a behavioral effect as well: acupuncture at Ht-7 significantly increased the time the rats spent in the open arms of a plus-shaped maze that was elevated 50 cm above the ground. This test is based on a natural fear of open and elevated spaces in rodents, so the number of entries into open arms and the time spent in open arms are negatively correlated with the anxiety level of the rats.

These results suggest that acupuncture at Ht-7 directly affects Neuropeptide Y function. This finding adds to previous results of the same group of scientists that showed the effect of Ht-7 on corticotropin-releasing factor (CRF), another neurotransmitter involved in stress response. Overall, these studies show that acupuncture at Ht-7 directly affects a network of neurotransmitters and may regulates their activity.

Interestingly, Pc-6 which is also used in TCM for treating mental disorders including anxiety, exhibits different effects in this rat model and did not influence the neurotransmitters levels. These findings support the notion that acupuncture produces meridian-dependent effects which are mediated by specific mechanisms and emphasize the importance of careful selection of points.

This paper clearly shows the effect of Ht-7 on the stress response in the brain. It would be interesting to find out how often Neuropeptide Y is involved in the mechanism of anxious states in humans. It would also be interesting to investigate whether acupuncture at Ht-7 can be used for preventing the induction of anxiety.